1. Field of the Invention
The present invention relates to a copier, laser printer, facsimile apparatus or similar image forming apparatus. More particularly, the present invention relates to a charge for charging a desired member in the vicinity of the member and a process cartridge using the same.
2. Description of the Background Art
It is a common practice with an image forming apparatus to charge a photoconductive element or image carrier with either one of a contact type charger and a non-contact type charger. A corona charger, for example, is a typical non-contact type charger and implemented as a corotron charger or a scorotron charger. The corona charger effects corona discharge by being applied with a voltage as high as 5 kV to 10 kV. A problem with the corona charger is that impurities deposit on the electrode of the charger due to the high voltage and discharge. Another problem is that sputtering and oxidation ascribable to the collision of active substances, which are produced by ionization, deteriorate the electrode of the charger, thereby producing ozone. Ozone is hazardous to the human body and environment and deteriorates various parts arranged in the image forming apparatus. Further, ozone and nitrogen oxides ascribable to the discharge deposit on the photoconductive element, bringing about irregular images and other defective images.
The contact type charger is generally implemented as a charge roller. While a charge roller also effects corona discharge, discharge is confined in a gap as small as 100 xcexcm or less and reduces the amount of ozone and other active substances to about one-tenth of the amount particular to the corona charger. However, it is likely that smears on the photoconductive element are transferred to the charge-roller, which is held in contact with the photoconductive element. The smears and scratches ascribable thereto are apt to make charging defective, causing white stripes and other defects to appear in an image.
Japanese Patent Laid-Open Publication No. 8-272,194, for example, teaches a proximity type charging system for obviating defective charging. The proximity type charging system uses a charging member including a conductive support formed of metal or an insulator coated with metal or conductive paint. The support is covered with a resistance layer implemented by polypropylene, polyethylene or similar resin or silicone rubber or similar rubber in which a conductive filler is dispersed. For the conductive filler, use is made of titanium oxide, carbon powder or metal powder by way of example. An AC bias is applied to the charging member for thereby effecting proximity type of charging. Further, a plurality of charging members are arranged around a photoconductive drum to thereby enhance efficient charging. However, even the proximity type charging system cannot fully obviate ozone.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 9-138543 and 11-327255.
It is an object of the present invention to provide a charger capable increasing charging efficiency to thereby reduce required energy as well as ozone and achieving a long life by effecting non-discharge, non-contact type of charging, and a process cartridge using the same.
A charger of the present invention includes a charging member for charging a desired member. The charging member is made up of a conductive support and a film formed on the support and formed of a substance having negative electron affinity (i.e., is not attracted to electrons).
A process cartridge using the above charger is also disclosed.